Graphite nanoplatelets and compositions

Abstract

Disclosed are graphite nanoplatelets produced by a process which comprises thermal plasma expansion of intercalated graphite to produce expanded graphite followed by exfoliation of the expanded graphite, where the exfoliation step is selected from ultrasonication, wet milling and controlled caviation and where greater than 95% of the graphite nanoplatelets have a thickness of from about 0.34 nm to about 50 nm and a length and width of from about 500 nm to about 50 microns. The intercalated graphite is intercalated for example with a mixture of sulfuric and nitric acids. The plasma reactor for example employs an RF induction plasma torch. All three exfoliation methods are performed in an organic solvent or water. The exfoliation steps may be performed with the aid of for example a nonionic surfactant. Also disclosed are plastic, ink, coating, lubricant or grease compositions comprising the graphite nanoplatelets.

1 . Graphite nanoplatelets produced by a process which comprises
 thermal plasma expansion of intercalated graphite to produce expanded graphite followed by   exfoliation of the expanded graphite,   where the exfoliation step is selected from ultrasonication, wet milling and controlled caviation and   where greater than 95% of the graphite nanoplatelets have a thickness of from about 0.34 nm to about 50 nm and a length and width of from about 500 nm to about 50 microns.   
     
     
         2 . Graphite nanoplatelets according to  claim 1  where the intercalated graphite is intercalated with a mixture of sulfuric and nitric acids. 
     
     
         3 . Graphite nanoplatelets according to  claim 1  where the expansion ratio achieved in the thermal plasma expansion is greater than 80 and where the specific density of the expanded graphite is from about 0.01 to about 0.006 g/cc. 
     
     
         4 . Graphite nanoplatelets according to  claim 1  where the BET surface area of the expanded graphite is from about 60 to about 600 m 2 /g. 
     
     
         5 . Graphite nanoplatelets according to  claim 1  where the exfoliation step is ultrasonication. 
     
     
         6 . Graphite nanoplatelets according to  claim 1  where the exfoliation step is wet milling where the size of the grinding beads is from about 0.15 mm to about 0.4 mm and the beads are zirconia, glass or stainless steel. 
     
     
         7 . Graphite nanoplatelets according to  claim 1  where the exfoliation step is controlled cavitation. 
     
     
         8 . Graphite nanoplatelets according to  claim 1  where the exfoliation step is performed in an aqueous or organic solvent. 
     
     
         9 . Graphite nanoplatelets according to  claim 1  where greater than 90% of the nanoplatelets have a thickness of from about 3 nm to about 20 nm and a width of from about 1 micron to about 30 microns. 
     
     
         10 . Graphite nanoplatelets according to  claim 1  where 95% of the nanoplatelets have an aspect ratio of at least 50. 
     
     
         11 . A composition comprising a plastic, ink, coating, lubricant or grease substrate, which substrate has incorporated therein graphite nanoplatelets,
 where the graphite nanoplatelets are produced by a process which comprises   thermal plasma expansion of intercalated graphite to produce expanded graphite followed by   exfoliation of the expanded graphite,   where the exfoliation step is selected from ultrasonication, wet milling and controlled caviation and   where greater than 95% of the graphite nanoplatelets have a thickness of from about 0.34 nm to about 50 nm and a length and width of from about 500 nm to about 50 microns.   
     
     
         12 . A composition according to  claim 11  comprising a plastic substrate. 
     
     
         13 . A composition according to  claim 11  comprising a plastic substrate selected from polypropylene, polyethylene and polystyrene. 
     
     
         14 . A composition according to  claim 11  comprising an ink or a coating substrate. 
     
     
         15 . A composition according to  claim 11  comprising a lubricant or a grease substrate. 
     
     
         16 . A composition according to  claim 11  comprising from about 0.1 to about 20 weight percent graphite nanoplatelets based on the weight of the substrate. 
     
     
         17 . A composition according to  claim 11  where the exfoliation step is ultrasonication. 
     
     
         18 . A composition according to  claim 11  where the exfoliation step is wet milling where the size of the grinding beads is from about 0.15 mm to about 0.4 mm and the beads are zirconia, glass or stainless steel. 
     
     
         19 . A composition according to  claim 11  where the exfoliation step is controlled cavitation. 
     
     
         20 . A composition according to  claim 11  where greater than 90% of the nanoplatelets have a thickness of from about 3 nm to about 20 nm and a width of from about 1 micron to about 30 microns.